"Donald Macpherson" was the pseudonym, used on two novels, of the British-born academic George* Humphrey, the son of Edmund Humphrey and his wife Emily Anne Maddex. He had a younger sister Dora Humphrey. He was educated at Queen Elizabeth's School, Faversham, and All Souls College, Oxford (1909, Honour Mathematical Moderations; 1912 Literae Humaniores). After graduating from Oxford he was awarded a Cassell scholarship to the University of Leipzig, where he studied experimental psychology under Wilhelm Wundt. From 1916 to 1918 he taught classics at St. Francis Xavier University in Nova Scotia, Canada, and from there moved on to Harvard University, where he received a PhD. in psychology in 1920. He was an assistant professor of psychology at Wesleyan University in Connecticut from 1920 to 1924, then in 1924 he was appointed the Charlton Professor of Philosophy at Queen's University on Kingston, Ontario, a post he held until 1947, when he became the first professor of psychology at the University of Oxford. He retired in 1956, moving to Cambridge, where he died in 1966.
Humphrey's professional works include The Story of Man's Mind (1923), The Nature of Learning in Its Relation to the Living System (1933), Directed Thinking (1948) and Thinking: An Introduction to Its Experimental Psychology (1951). With his first wife, Muriel Miller Humphrey, whom he married in 1918 and with whom he had one daughter, he translated Jean-Marc-Gaspard Itard's early nineteenth-century account of the case history of a French feral child discovered around the year 1800 (at the estimated age of twelve). The translation was published as The Wild Boy of Aveyron (1932). Muriel Humphrey died in 1955, and in the following year George Humphrey married his colleague Berta Hochberger.
In The Dictionary of Modern American Philosophers (2005), edited by John R. Shook, Humphrey's professional publications are assessed as follows:
The pattern of Humphrey's lifetime research reflected his concern with integrating the separate approaches of the various schools. In writing The Story of Man's Mind, he had found that he could not deliver a popular account of problem solving by adults, or even of the normal flow of adult mental associations, without recourse to the notion that all thought was guided by motives of some kind. In a second popular book, Direct Thinking (1948), he suggested that psychoanalysis might provide a rationale whereby even conflicting thought processes could be shown to have an underlying logical structure if the motives underlying them possessed common elements. Humphrey's Thinking (1951) is the most detailed account in English of the research on human mental problem solving that had been carried out in Germany by the Würzburg School, by Otto Selz, and by the Gestalt psychologists. Their experiments all demonstrated the importance of motivation ("set") in determining the sequence of thoughts.The two Donald Macpherson novels come directly out of Humphrey's professional work. At their simplest, they are novels which experiment in methods of using the mind to manipulate matter. Both center around four main protagonists: Reginald Brooks, who works at a Montreal private experimental scientific think-tank, the McDuffie Institute; George MacTavish, a journalist who became friends with Brooks when they were both at Oxford; Olive Paynter, a distinguished scientist herself and Montreal society debutante, and the fiancée of Brooks; and Mary Raiche, another eligible society woman who had gone to school with Olive. In Go Home, Unicorn (London: Faber and Faber, 1935), Brooks and his friends study some bizarre phenomenon, including a man who has seen a disembodied hand come through an open window of his car, causing an accident; in another instance a woman's severed head angrily manifests itself at a dinner party; in another, a celebrated composer directing his own "Hymn of Hate" is flung violently across the stage as a result of the audience's reaction; and subsequent to two of the characters attending a lecture on Mythological Animals, an angry unicorn manifests itself to the danger of all. Only the presence of Mary Raiche calms the animal, and its rage at Olive Paynter forces her to admit sexual indiscretions in her past, and she withdraws from the intended marriage to Brooks. The solution to the supposed hauntings turns out to be quite silly. At the McDuffie Institute, Brooks's research involves radiating guinea pigs, and the altered states of the minds of the guinea pigs is determined to have caused the hauntings. As a novel, Go Home, Unicorn has considerable problems: the characters are wooden, much of the heavy dialogue is either humorless banter irrelevant to the story or Brooks's info-dumps of his ongoing analysis of the case, given to set up the next plot moves of the characters in their attempt to solve the mysteries. Yet despite these and other flaws (ranging from dated sexism to nonscientific explanations), the story is readable and compelling primarily because what keeps happening is unusual and unexpected. Oddly, in the final chapter, after Brooks has explained the situation, a strange and seemingly-evil tentacled thing appears on the ceiling at the McDuffie Institute, giving the novel it's most intriguing development—yet this happens after the mysteries have been explained. (The book appears to switch genres with this last section, going from a light comedic fantasy to unrestrained horror. The only other book I can think of like this is Michael Arlen's Hell! Said the Duchess, published in 1934.)
The second novel, Men Are Like Animals (London: Faber and Faber, 1937) is a direct sequel to the first, taking place something over a year after the events of the first novel. Brooks and Mary Raitch are married, but Olive has put together some sort of electrical machinery that amplifies and alters human emotions from a distance, so much so that Mary Brooks is lured into infidelity with George MacTavish. Olive is seeking to get Brooks back, but things do not work out as she had planned. Again the same flaws appear in the novel, and the again it's the sheer unusualness of the plot and straightforward readability of the prose that keeps one going to the end. Damien Broderick, in his Psience Fiction (2018), counts Go Home, Unicorn as one of the earliest novels of telepathy or psi powers.
*Internet resources give "William" as a middle name, but none of the genealogical and printed sources I have consulted corroborate this, and his birth and baptism registrations include no middle name.